This invention relates to a tilt device for a marine propulsion unit and more particularly to an improved and simplified method of forming the housing assembly for such a unit.
Various tilt and trim devices have been proposed for hydraulically controlling the position of a marine propulsion unit. These devices may provide either trim or tilt up operation or a combination of them. The device is generally mounted as a unit between the watercraft hull and the propulsion unit and has one or more fluid motors that cooperate with the propulsion unit to adjust its position. Obviously it is desirable to provide a compact assembly and nevertheless, one which is capable of providing the desired control for the propulsion unit.
Generally these units include one or more tilt and/or trim cylinders, a reversible electric motor, a reversible hydraulic pump driven by the electric motor and a control valve assembly for controlling the flow of fluid from a reservoir to the pump, from the pump to the cylinder or cylinders and a return from these cylinders to the reservoir. Obviously this requires a number of passages to be formed in the housing assembly.
Generally the housing assembly is a cast member and the various passages are formed by drilling the casting. Where angularly related passages are required, they are provided by cross drillings with the resulting open ends of certain of these drilling being plugged to provide desired fluid path.
A disadvantage results from the use of these multiple drilled passages. That is, the machining operation can leave foreign particles in the body even though cleaning operations are performed after the drilling has been completed. These foreign materials can mix with the hydraulic fluid and can in extreme instances cause problems in operation. Furthermore, they can decrease the durability of the unit.
It is, therefore, a principle object to this invention to provide an improved marine propulsion control device of this type wherein the number of drilled passages can be substantially reduced.
It is a further object to this invention to provide an improved construction and method for forming passages in an device of this type.
A first feature of this invention is adapted to be embodied in a cast housing for a hydraulic tilt and trim arrangement for a marine propulsion device. The cast housing defines a cylinder for receiving a piston for controlling the position of the marine propulsion device, a fluid reservoir for containing a fluid, a pumping chamber for containing a fluid pump, a valve chamber for containing a control valve and a conduit for communicating the fluid reservoir with the valve chamber, the valve chamber with the cylinder and the valve chamber with the pumping chamber. At least a portion of the conduit is formed by a pipe that is molded into the cast housing when the cast housing is molded to minimize drilled passages in the cast housing.
Another feature of the invention is adapted to be embodied in a method for forming a cast housing as set forth in the previous paragraph. In accordance with this method, a pipe is formed in a desired configuration and the pipe is molded into the cast housing when the cast housing is molded so as to minimize the drilled passages.